Hidden deep in a forest is this geological wonder carved by glaciers.

Finland's oldest astronomical observatory once played a crucial role in seafaring and timekeeping.

Pigduck of Turku.

The tiny, studious rodents greet visitors to the National Archives of Finland.

A small island dotted with old, historic Finnish buildings.

This irregularly shaped sea fortress has defended not one but three different sovereign states.

Ancient human, animal, and geometric figures drawn in the earth.

This bridge was constructed from the rubble of the infamous Bastille.

The hottest place on the planet.

The floor of the oldest surviving synagogue in the Americas is entirely covered in sand.

The world is full of swimming holes, but few compare to Samoa’s idyllic To Sua ocean trench.

The ship that got left behind.

A historic scientific breakthrough that crosses nine borders.

Six times a day a train runs right through the middle of this Thai street market, sending vendors scrambling.

A backdoor to Machu Picchu that only the most foolhardy infiltrator would attempt to breach.

The world's tallest bridge is also possibly the most elegant.

An unusual cave filled with rare alien-looking aragonite formations.

Celebrated as a center of civilization, the remains of the ancient city have been nearly destroyed by greed, egoism, and war.

9th century Abbasid mosque, damaged in modern warfare.

The sacred shrine of the Yazidis.

Monasteries on rock pillars, once accessible only by frayed ropes.

A 15th-century granary that played the role of futuristic slave quarters in the world of 'Star Wars.'

Landscape of bizarrely shaped desert mountains and innumerable rock carvings.

The abstract sandstone rock formations at this Algerian national park are rich with prehistoric art.